In a cellular broadband wireless communication system, each of a plurality of BSs performs communication through a wireless channel with a Mobile Station (MS) located in its own coverage. Typically, a state of the wireless channel varies depending on the movement of the MS. When the MS is located in a physically sealed area, for example, in a propagation shadow area such as an office or a house, a channel between the BS and the MS is greatly deteriorated and hence, smooth communication cannot be carried out. Hence, as one alternative for solving this, a scheme for installing an indoor BS acting as BS in a small indoor shadow area such as an office or a house is being considered.
The use of the indoor BS provides an advantage of being capable of providing service in a shadow area, but there is a concern that interference with a macro BS will be generated because the indoor BS is installed within the coverage of the macro BS. Hence, in using the indoor BS, the control of the Transmit power (TX power) of the indoor BS should follow the two conditions below:
First, the amount of a signal leaking out a building should be minimized so as to minimize interference; and
Second, capacity in guaranteed indoor coverage should be maximized.
The less the TX power is, the easier the first condition is met. The more the TX power is, the easier the second condition is met. That is, the above two conditions are in conflict with each other. Therefore, an alternative for maximizing the efficiency of an indoor BS by meeting the above two conditions should be presented.